Process for preparing a



PROCESS FOR PREPARING a,w-DINITROALKANES Henry Feuer, Lafayette, Ind., and Christos Savides,

Somervilie, N .J assignors to Purdue Research Foundation, Lafayette, Ind., a corporation of Indiana No Drawing. Filed May 8, 1959, Ser. No. 811,799

2 Claims. (Cl. 260-1944) Our new process relates to the preparation of nitroalkanes and more particularly to a process for the preparation of a,w-dinitroalkanes from a,a-dinitroalkanedinitriles.

Previously a,w-dinitroalkanes have been prepared by the process described in Organic Synthesis, vol. 34, p. 37, John Wiley and Sons, New York, New York, 1954. In this process, a,-w-alkanedihalides are reacted with silver nitrite to form the desired dinitroalkanes and a silver halide.

We have now discovered that the alkali metal and alkaline earth metal salts of a,ot-dinitroa1kane dinitriles can be hydrolyzed by alkali metal and alkaline earth metal hydroxides to form t,0L'-d1Il1tI'Od1CafbOXy11C acid salts. These salts are then decarboxylated to obtain the desired a,w-dinitroalkane by reacting the salt with a weak acid at low temperatures. Weak acids which are useful for this purpose include lower fatty acids, such as formic, acetic, propionic, etc.; and inorganic acids, such as boric, phosphoric, etc.

The salts of a,a'-dinitroalkane dinitriles useful in our invention include the alkali metal and alkaline earth metal salts of any of the alkane dinitriles, preferably those containing up to about 20 carbon atoms. Such nitriles include 1,6-hexanedinitrile, 1,7-heptanedinitrile, 1,5-pentanedinitrile, B-methylpentanedinitrile, 3-ethylpentanedinitrile, 3-hexylpentanedinitrile, adiponitrile, 3-methyladiponitrile, 4,4-dimethylheptanedinitrile, 1,8-octanedinitrile, 1,9-nonanedinitrile, 1,10-decanedinitrile, l,ll-undecane dinitrile, 1,12-dodecanedinitrile, 1,13-tridecanedinitri1e, 3- methyltetradecanedinitrile, 3 methylpentadecanedinitrile, 3,13 dimethylpentadecanedinitrile, 4-rnethylhexadecanedinitrile and 3,14-dimethylhexadecanedinitrile, etc.

While we can use any of the alkali metal or alkaline earth metal salts of a,a-dinitroalkanedinitriles in our process, we have found that in some instances the alkaline metal salts give the higher yields. For example, using the potassium salt of a, x'-dinitroadiponitrile of Example II below, we obtained a 32% yield, as compared to a yield of only 19% when using the corresponding barium salt under the same operating conditions.

The alkaline hydrolysis of the metal salts of u,a'-dinit10- alkane dinitriles is carried out at temperatures ranging from about 75 to about 135 while the acid decarboxylation step is carried out at temperatures of about 20 to about 10 C. The alkaline hydrolysis is slow even at our preferred temperatures of about 90-110 and it is preferable to pass large amounts of steam through vigorously stirred solutions of the dinitro substituted nitriles to increase the reaction rate. The acid decarboxylation step is violent at temperatures above 10 C. and we prefer to carry out this reaction at temperatures of about 10 to about +5 C.

While the hydrolysis of nitriles to the corresponding acids in acidic or basic media is well known, we have found that acidic hydrolysis of a,ot'-dinitronitriles does not give the expected a,w-dinitroalkanes but instead intractable oils. We have further found that in basic medium a,w-dinitro compounds are not obtained unless cer- 2,963,515 Patented Dec. 6, 1960 tain conditions are employed. Thus, when the reaction was carried out in 25% boiling potassium hydroxide, the evolution of ammonia was fast, but acidification did not cause decarboxylation and no water insoluble material was obtained (a,w-dinitroalkanes are water insoluble). When the hydrolysis was repeated at 70 C., six days were required for complete evolution of ammonia. This extended heat treatment again caused decomposition of the starting material, because no water insoluble products could be isolated upon acidification with either dilute hydrochloric acid or glacial acetic acid. It was only when heating the salt of the u,a'-dinitronitrile with a base at temperature ranging from about to about 135 C. while passing steam through the reaction mixture, followed by slow neutralization of the cooled reaction product, when the desired a,w-dinitroalkane was obtained in practical yields.

The following examples more fully illustrate our invention.

Example I Adiponitrile (5.4 g.) was added to a solution of 18.5 g. of sublimed potassium t-butoxide in ml. of purified tetrahydrofur-an at -50 C. Amyl nitrate (14.6 g.) was then added to the reaction mixture very slowly at 45 to 50 C. After the addition of the amyl nitrate the reac tion mixture was allowed to warm to room temperature. The solid formed was filtered through a pressure filtration apparatus under nitrogen. The residue was Washed with 30 ml. of anhydrous diethyl ether and 30 ml. portions of tetrahydrofuran, absolute ethanol, and a mixture of 15 ml. of absolute ethanol and 15 ml. of methanol. The crystals were then dried in vacuo over sulfuric acid to give a 93% yield (13.0 g.) of dipotassium a,a'-dinitroadiponitrile.

Example II To a 7.5% aqueous potassium hydroxide solution was added 7.5 g. of dipotassium ut,a'-dinitroadiponitrile from Example I. The stirred solution was heated to 90 and steam was passed through the reaction mixture until ammonia evolution was complete. This required about 18 hours. The reaction mixture was cooled to 0 C. and glacial acetic acid was added, d-ropwise, until carbon dioxide evolution ceased. The mixture was extracted with ether in a liquid-liquid extraction apparatus and the ether extract was evaporated in vacuo. The residual oil was dissolved in 10 ml. of 95% ethanol and cooled to Dry Ice temperatures to give 1.20 g. (32% yield) of 1,4-dinitrobutane.

Example III 1,7-heptanedinitrile was nitrated as described in Example I and converted to 1,5-dinitropentane, B.P. 134/ 1.2 mm., n 1.461 as described in Example 11.

Example IV 1,8-octanedinitrile was nitrated as described in Example I and hydrolyzed as described in Example II to 1,6-dinitrohexane, M.P. 36.5-37.5.

Example V 1,5-pentanedinitrile was converted to 1,3-dinitropropane, B.P. 108110/ 1 mm., n 1.465 as described in Examples I and II.

Example VI 1,10-decanedinitrile was nitrated as shown in Example I and the resulting salt hydrolyzed as indicated in Example II to 1,8-dinitr0octane, M.P. 36-365.

Example VII Dipotassium a,a-dinitrononanedinitrile, prepared from 1,9-nonanedinitrile as indicated in Example I, was con.

Example VIII Dipotassium a,ot dinitroundecanedinitrile prepared from 1,11-undecanedinitrile as described in Example I was hydrolyzed to 1,9-dinitrononan c, B.P. 141a-142/0.2 mm, n 1.4598, d 1.0729 as described in Example II.

Now having described our invention what we claim is:

1. In a process for the preparation of a,wdinitroalkanes, the steps which comprise contacting a dinitro salt of an alkane dinitrile selected from the group consist,- ing of the alkali and alkaline earth metal saltsof mud-dinitroalkanedinitriles with a base at temperatures of from about 75 to about 135 C. to form a,a'-dinitrodicarboxylic acid salts, cooling the dicarboxylic acid salts to from about -,-2O to about 10 C., contacting the resulting dicarboxylic acid salts with a weak acid, and recovering the a,w-dinitroalkanes thereby formed.

2. In a process for the preparation of a,w-dinitro- .alkanes, the steps which comprise contacting .a dinitro salt of an alkane dinitrile selected from the group consisting of the alkali and alkaline earth metal salts of a,cc'-dinit10- alkanedinitriles with a base selected from the group consisting of alkali metal and alkaline earth metal hydroxides, passing steam through the reaction mixture while maintaining the mixture at temperatures of from about 90 to about 110 C. to form the a,a'-dinitrodicarboxylic acid salts, cooling the said dicarboxylic acid salts to from about 10 to about 5 C. and contacting the said dicarboxylic acid salts with a weak acid.

References Cited in the file of this patent Weygand: :Organic Preparations, pages 292-93, 445, Interscience Publishers, Inc., N.Y. (1945).

Brewster: Organic Chemistry, pages 141-2, Prentice Hall, Inc., N.Y. (1949).

Degering: An Outline of Organic Nitrogen Compounds, page 510, Univ. Lithoprinters, Ypsilanti, Mich. 

1. IN A PROCESS FOR THE PREPARATION OF A,W-DINITROALKANES, THE STEPS WHICH COMPRISE CONTACTING A DINITRO SALT OF AN ALKANE DINITRILE SELECTED FROM THE GROUP CONSISTING OF THE ALKALI AND ALKALINE EARTH METAL SALTS OF A,A''-DINITROALKOANEDINITRILES WITH A BASE AT TEMPERATURES OF FROM ABOUT 75 TO ABOUT 135*C. TO FORM A,A''-DINITRODICARBOXYLIC ACID SALTS, COOLING THE DICARBOXYLIC ACID SALTS TO FROM ABOUT -20 TO ABOUT 10*C., CONTACTING THE RESULTING DICARBOXYLIC ACID SALTS WITH A WEAK ACID, AND RECOVERING THE A,W-DINITROALKANES THEREBY FORMED. 